Technology and Market Trends
The evolution of telecommunications in general and of packet switching networks in particular is driven by many factors among which two of them worth emphasizing: technologies and applications.
Emerging Technologies
Communication technologies have realized these last years considerable progress with:
the maturing of new transmission media and specially of optical fiber. High speed rates can now be sustained with very low bit error rates. For example, the very important bandwidth provided by optical connections, their low attenuation and their high transmission quality are turned to account as well as for long distance networks as for high rate local networks. PA1 the universal use of digital technologies within private and public telecommunications networks. PA1 a very large flexibility to support a wide range of connectivity options, PA1 a very high throughput and a very short packet processing time, PA1 an efficient flow and congestion control. PA1 the flow control for regulating the emitting data rate of the calling subscriber at a rate compatible with what the receiver can absorb. PA1 the load regulation for globally limiting the number of packets present in the network to avoid an overloading of the resources, and PA1 the load balancing for fairly distributing the traffic over all the links of the network to avoid a local congestion in particular resources. PA1 a network routing control traffic, and PA1 a network signalling control traffic. PA1 irrespective of the link capacity and of the actual use. PA1 without considering whether links belong to network Spanning Tree or not (Links on the Spanning Tree have to transmit all the routing control traffic, mainly Topology Update messages). PA1 Connection setup and connection takedown messages, PA1 Connections bandwidth refresh messages, PA1 Connections bandwidth adaptation (increase/decrease) messages, PA1 Directory queries in network (directed to a specific resource), . . . PA1 network Spanning Tree have to support. PA1 Control Point Spanning Tree maintenance messages, PA1 Topology Update messages, PA1 Directory searches in network (broadcast through the network), . . . PA1 first, dynamically estimating, for each link, the bandwidth fraction necessary and sufficient for transmitting the network routing and signalling control packets on said link, and PA1 secondly, reserving said estimated bandwidth fraction on each link. PA1 the number of connections on the link, PA1 the network routing control traffic for distributing topology information between nodes of the network, PA1 the number of links within the network for a transmission link belonging to a network control spanning tree.
The emergence of high speed transmission entails an explosion in the high bandwidth connectivity. The advent of these new technologies has pushed the speed of communication links to the area of the giga-bit per second representing an increase of several orders of magnitude over typical links in traditional networks. The increase in communication capacity is generating more attractive tariffs and large bandwidths are economically more and more attractive.
New Applications
On the other hand, in relation with these new emerging technologies, many potential applications that were not possible before are now becoming accessible and attractive. In this environment, three generic requirements are expressed by the users:
Improving Old Applications
Sub-second response times, which are achievable on low cost personal computers, have raised user expectations so that the lengthy wide area networks response times that were acceptable some years ago are today no longer tolerable. The user interface can be bettered, for example, with fast response full screen applications.
Optimizing Communication Networks
There is a need for rationalizing the many disparate networks that major users have. Investments can be optimized by integrating heterogeneous traffics like voice, video, and data over the same transport facilities regardless of protocols. Users want the opportunity to control their networking cost by choosing among the different price/performance options offered by the variety of vendors and carriers and to maximize their ability to take advantage of applications built on top of disparate underlying network technologies. However, the motivation for rationalization this is not only to save money on links but also to provide a better networking service by integrating the many disparate networks into a single coherently managed unit.
Doing New Applications
Emerging applications like graphic, image, video, and multimedia processing are requiring a very large volume of traffic. These new applications that were not feasible (or indeed imaginable) before are now becoming accessible generating an ever-increasing demand on bandwidth.